One of the great advances of the nineteenth and twentieth centuries was the realization that improper treatment of human and other animal waste leads to pollution of otherwise potable water supplies and to disease. Sewage treatment systems sprang from this realization. There are two kinds in common residential, business and light industrial use.
The first kind is the municipal sewage system, in which all of the residences, businesses and institutions in a municipality are connected through a network of sanitary sewers to a central sewage treatment plant. After treatment, the wastewater is discharged into a river or other body of water. Often, this water has high nutrient levels, leading to undesirable eutrophic activity in the body of water into which the effluent is discharged, producing algal blooms, decreased oxygen concentration levels, fish kills and undesirable odors. Another byproduct of the typical municipal sewage system is sludge, which must be hauled away for incineration, burial in a landfill or dumping at sea--and which, in the course of being disturbed, emits a highly objectionable odor.
The second kind is the septic system, typically installed for single residences in unincorporated locations where connection to a sanitary sewer is unavailable. Even properly designed septic systems still have some objectionable wastewater discharge, and since septic systems are usually installed in tandem with wells for drinking water, care must be taken that a septic system discharge does not contaminate the potable well water of the same property or of adjacent properties. The septic system wastewater is not put to any beneficial use, and sludge accumulates in the septic tank of the system, requiring periodic removal. Septic systems, therefore, have the same environmental problems relating to sludge handling that the municipal sanitary sewer systems do.
Other wastewater treatment systems have been devised for large-scale, typically industrial use. Currently the smallest wastewater reclamation and reuse system which is permitted by the environmental protection agency in one state (Illinois) is 3,100 gallons per day and employs multiple cells. In a modular reclamation and reuse system previously developed by the inventor, wastewater is sent to a first treatment pond or cell, where it is aerated by the injection of air at the 10 bottom of the pond. After residing in the pond for a number of days sufficient to cause anaerobic degradation of biomass and aerobic disinfection of the water, the treated wastewater is sent to a second, holding pond. The wastewater is eventually released for beneficial use, such as crop irrigation or the watering of golf courses. This two-cell system occupies of great deal of land area.
To date, however, no system of this type has been used as a replacement for a septic system or other small-scale wastewater treatment system. In fact, to the inventor's knowledge, none of the public health codes of the 50 states contemplates such a use. Because of continuing problems of sludge disposal, incomplete wastewater treatment and inefficient water use, a need persists for improved wastewater treatment systems in which better use can be put to the treated wastewater.